Iterating over Lists of Lists OR Creating Nested For loops in Python

Lets say you have a list of lists containing values that you want to iterate over. The problem is that the number of lists keeps on changing so you can’t really make it into a hard coded set of nested for loops. What you really need is to dynamically create a set of nested for loops. In Python you can use the itertools for these kind of jobs. Extremly handy if you want to do grid search over a set of values for example. In code it might look like this,

# Python3
import numpy as np 
from itertools import product

# Create a list of np array values  
rangeList = []
rangeList.append(np.linspace(0.,10.,10))
rangeList.append(np.linspace(40.,1000.,10))
rangeList.append(np.linspace(10.,40.,10))

# Iterate over all of the lists values 
for vals in product(*rangeList):
    for val in vals:
        print(val,end=",")
    print(" ")

this will print the following,

>>  0.0,40.0,10.0,
    0.0,40.0,13.3333333333,
    0.0,40.0,16.6666666667,
    0.0,40.0,20.0,
    0.0,40.0,23.3333333333,
    0.0,40.0,26.6666666667,
    ....